Heat pump including drain pan heating means



Oct. 11-, 1960 INVENTOR. GEORGE R. PINTER H (S ATTGRNIY s. R. PINTER 2,955,439" 1 um PUMP mcwnmc mum PAN HEATING mus Filed llay-26, 1958 States Patent Patented Oct. 11, 1960 HEAT PUMP INCLUDING DRAM PAN HEATING MEANS George R. Pinter, Caldwell, N.J., assignor to General Electric Company, a corporation of New York Filed May 26, 1958, Ser. No. 737,879 5 Claims. (Cl. 62-278) The present inventionrelates broadly to heat pumps and is more particularly concerned with a heat pump including heating means for maintaining portions essential for proper drainage of the drain pan structure associated with the outdoor heat exchanger component of the heat pump above freezing temperatures during operation of the pump on the heating cycle and thereby preventing freeze-up of this structure.

Heat pumps employed for cooling a dwelling or other structure in the summer and for the'heating thereof during the colder months essentially comprise a reversible refrigeration system including an indoor heat exchanger, a compressor, an outdoor heat exchanger, and flow control means for between the two exchangers during operation of the compressor. Operation of a heat pump on the heating cycle involves the absorption of heat from the outdoor air by the refrigerant circulating through the outdoor heat exchanger and the liberation of this to the air passing over the indoor heat exchanger. During the heating cycle operation, the outdoor heat exchanger, which functions as an evaporator, must of course operate at a lower temperature than the surrounding air from which heat is being extracted with the result that under certain climatic conditions frost may accumulate on this component. A layer of frost reduces the ef ficiency of the system to such an extent that it is necessary to periodically remove and dispose of the frost accumulation. To accomplish the removal of the acproviding a pressure differential or drop In carrying out the objects of the present invention, there is employed a heat pump including a reversible refrigerating system including a compressor, an indoor heat exchanger, an outdoor heat exchanger, and flow control means between the two heat exchangers for providing a pressure differential between the two heat ex changers. For operation of the refrigerating system on the heating cycle with the outdoor heat exchanger functioning as an evaporator, the compressor, the indoor heat exchanger, the flow cont-r01 means and the outdoor heat exchanger are connected in closed, series-flow connection so that the compressor withdraws low pressure refrigerant from the outdoor heat exchanger and discharges high pressure refrigerant to the indoor heat exchanger.

A drain pan is provided below the outdoor heat exchanger for receiving and disposing of frost, which in liquid or solid form, drops from the outdoor heat exchanger during the periodic defrosting thereof. In order to assure disposal of the contents of the pan and to melt any solid frost or ice removed from the heat exchanger, a portion of the refrigerating system which operates at a high pressure during operation of the heat pump on the heating cycle is arranged in heating relationship with the drain pan so that the warm high pressure refrigerant flowing from the compressor to the flow control means between defrost periods maintains the drain pan at above freezing temperatures. In the preferred form of the invention the drain pan is warmed by means of a coil forming part of the liquid line conducting warm-high pressure refrigerant from the indoor coil to the flow control means during operation of the system on the heating cycle.

For a better understanding of the invention reference may be had to the accompanying drawing in which:

Fig. 1 is a somewhat diagrammatic illustration of the heat pump'installation embodying the present invention; and a Fig. 2 is a sectional view of the part of the heat pump installation of drain pan forming Fig. 1 and illustrat- "xing a preferred arrangement for maintaining the drain cumulated frost and ice from the outdoor heat exchanger,

it is common practice to raise the temperature of the heat exchanger above the freezing point of water and to dispose of the melted frost by means including a drain pan provided below the heat exchanger. Since this drain pan is positioned close to the outdoor heat exchanger it is normally subjected to the same outdoor temperatures as the heat exchanger so that unless the defrost operation is relatively prolonged, below freezing outdoor temperatures may cause the accumulation of ice in the drain pan with the resulting freezing or plugging of the drain line connected thereto.

It is an object of the present invention to provide a heat pump including means for preventing freeze-up of the drain pan associated with the outdoor heat exchanger.

Another object of the present invention is to provide a heat pump including means for preventing freeze-up of the drain line associated with the drain pan of the outdoor heat exchanger. 7

Another object of the invention is to provide a heat pump including means forming part of the refrigerating circuit for maintaining the drain pan associated with the outdoor heat exchanger at above freezing temperatures during operation of the heat pump on the heating cycle.

Further objects and advantages of the invention will become apparent as the followingdescription proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

pan at above freezing temperatures.

Referring now to the drawing, the illustrated heat pump comprises a reversible refrigerating system which includes the indoor heat exchanger 1, an outdoor heat exchanger 2, a compressor 3, and a flow control means changed with the air circulated 4. -Bymeans of a reversing valve 5, the compressor may be so connected to the remaining portions of the refrigerating system that the indoor coil 1 will function as either an evaporator or as a condenser. For operation reversing or switch-over valve 5 effects flow of high pressure refrigerant from the compressor 3 to the indoor heat exchanger 1 functioning as warming the air to be conditioned which is circulated through the indoor heat exchanger 1 by a fan 7, suitable ducts S and 9 normally being provided for conducting the air from and to the enclosure being served by the heat pump. In the indoor heat exchanger 1 the refrigerant is partially or completely condensed by heat exchanger and this refrigerant then flows through the line 11 to the flow control means 4 which may be any of the usual flow control devices, such as an expansion valve or a capillary tube arrangement, for effecting a pressure drop or expansion of the refrigerant as it flows from the flow control means 4 to the outdoor heat exchanger 2. In the outdoor heat exchanger 2 which is operating as an evaporator during the heating cycle, heat is absorbed by the refrigerant from theoutdoor air circulated over this heat exchanger and intake 13 by means of a fan 12.

a condenser or as a heating coil for through that heat ex- When the system is reversed by means of the switch over valve 5 for operation as a cooling unit, the flow of refrigerant through the heat exchangers is reversed so that outdoor heat .exchangerl receives high pressure refrigerant from the compressor 3 and operates as a condenser While the indoor heat exchanger 1 receives low pressure refrigerant from the flow control means 4 and operates as an evaporator thereby cooling the air circulated by means of the fan 7 over this heat exchanger.

During the heating cycle operation of the heat pump, the outdoor heatexchanger 2 operating at temperatures below ambient, that is below outside air temperatures, frequently attains below freezing'temperatures with the result that frost accumulates on the surface thereof. Because of the insulating character of this frost layer, it is essential that it be removed periodically in order to maintain the proper operation of the system. For thtis pur! pose various heating means have been employed for periodically raising the temperature of the. outdoor coil to temperatures at which the frost will be removed from .the heat exchanger and collected in a drain pan 14 provided below the outdoor heat exchanger 2. Electrical heating by means of suitable resistance heaters and hot gas defrosting by means of hot compressed refrigerant from the compressor or .both are common arrangements for defrosting. the outdoor coil or heat exchanger of a heat pump. While the present invention is not restricted thereto, the outdoor heat exchanger 2 is preferably defrosted by operating this heat exchanger as a condenser, that is, by reversing the flow of refrigerant through the system so that hot gas from the compressor is fed to the outdoor heat exchanger.

During defrost operation most .of the frost on the outdoor heat exchanger 2 will melt and the resultant liquid flow into the drain pan 14. However, under relatively low outside temperatureconditions, unmelted frost or ice also may slide or drop from the heat exchanger into the outdoor drip pan.14 where it'is no longer in a position to be melted by the refrigerant flowing through the heat exchanger 2. Also, when the outdoor temperature is belowfreezing, the drain pan subjected to substantially the same outdoor temperature may also operate below freezing so that liquid condensate flowing from the outdoor heat exchanger 2 may freeze before it flows from the drain pan through the drain line 15. In either case, ice accumulation in the drain pan during successive defrost cycles may lead to a freeze-up of the drip pan and drain line thereby preventing further disposal of the defrost condensate.

In accordance with the present invention this ice accumulation is positively avoided by an arrangement in which the drain pan 14 is continuously heated during each heating cycle operation of the heat pump by high pressure refrigerant flowing through the system.

In accordance with the illustrated embodiment of the invention, this heating or warming of the drain pan 14 is obtained by arranging a portion of the refrigerant line 11 between the indoor heat exchanger and the flow control means 4 in heating contact with the drain pan 14- to form a drain pan heater 17. Preferably, also a part of the heater 17 is in close proximity to the opening of the drain line 15 to assure melting of any ice in the vicinity of the drain line. While in its broadest aspects, the inventioncontemplates the .use of any portion of the system carrying the high pressure refrigerant during the heating cycle for warming the drain pan, the line 11 is considered to be the most advantageous section since the use of this part of the high pressure side downstream from the indoor heat exchanger does not materially detract from the amount of heat available for the heating air circulated over the indoor heat exchanger.

The heat losses due to the exposure of the high pressure line to outside temperatures may be cut down by covering the drain pan heater 17 with a blanket of insulation 18 which either surrounds at least that surface area of the heater not in direct contact with the drain pan or which, as shown, surrounds the entire periphery, the thickness of the insulation between the heater and pan being such that only enough heat from the warm refrigerant flowing through the heater section 17 will be provided to maintain the drain pan and the drain line 15 at temperatures above freezing during operation of the system on the heating cycle.

By this arrangement, it will be seen that during each heating operation of the system and thereby While frost may again be accumulating on the outdoor heat exchanger 2, the refrigerant line 11 delivers, as by means of the drain pan heater 17, suflicient heat to the outdoor drain pan 14 so that any ice or unmelted frost which may have been deposited there from a previous defrost cycle is melted before the next defrost period. In addition, this heating of the drain pan between defrost cycles prevents freezing of any Water in the pan so that the disposition of allof the frost in the form of a liquid through the drain line 15 is assured.

It will be noted, of course, that the heater 17 operates as part of the low pressure side of the system during the defrost cycle when high pressure refrigerant is being provided by the compressor to the outdoor coil 2 which is then functioning as a condenser. This cooling of the drain pan 14 during the defrost operation has no appreciable effect on the condensate disposal problem since the defrost cycle is ordinarily very short as compared with the heating cycle with the result that any moisture frozen in the drain pan during the defrost cycle quickly melts during the subsequent heating cycle. During summer operation of the heat pump on the cooling cycle, the drain pan 14 is of course also cooled by the low pressure refrigerant from the flow control means 4. However, since the outdoor heat exchanger 2 is normally free of moisture during operation of the cooling cycle and the drain pan 14 is dry, there is no significant decrease in the efliciency of the system insofar as the cooling of the air directed over the indoor heat exchanger 1 is concerned.

While there has been shown and described a particular embodiment of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is intended by the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A heat pump comprising a reversible refrigerating system including a compressor, an indoor heat exchanger, flow control means and an outdoor heat exchanger, means connecting said compressor, indoor heat exchanger, flow control-means and outdoor heatexchanger in closed series flow connection for operation of said heat pump on the heating cycle whereby said compressor withdraws low pressure refrigerant from said outdoor heat exchanger functioning as an evaporator and discharges high pressure refrigerant to said indoor heat exchanger, means for periodically defrosting said outdoor heat exchanger, a

drain pan for collecting moisture and frost removed from said outdoor heat exchanger during defrosting thereof, and means for warming said pan during operation of said heat pump on the heating cycle comprising a refrigerant conduit in heating relation with said pan, said refrigerant conduit forming a part of said system carrying high pressure refrigerant during operation of said heat pump on the heating cycle.

2. A heat pump comprising a reversible refrigerating system including a compressor, an indoor heat exchanger, flow control means and an outdoor heat exchanger, means connecting said compressor, indoor heat exchanger, flow control means and outdoor heat exchanger in closed series flow :connection for operation of said heat pump on the heating cycle whereby said compressor withdraws low pressure with refrigerant from said outdoor heat exchanger functioning as an evaporator and discharges high pressure refrigerant to said indoor heat exchanger, means for reversing the flow of refrigerant whereby said outdoor heat exchanger. will function as a condenser for defrosting thereof, a drain pan for collecting moisture and frost removed from said outdoor heat exchanger during defrosting thereof, and a means for warming said pan during operation of said heat pump on the heating cycle comprising a refrigerant conduit in heating relation with said pan, said refrigerant conduit forming a part of said system between said indoor heat exchanger and said flow control means conducting high pressure refrigerant during operation of said heat pump on the heating cycle.

3. A heat pump comprising a reversible refrigerant system including an indoor heat exchanger, an outdoor heat exchanger, a compressor, a refrigerant line including flow control means for controlling the flow of refrigerant from either of said heat exchangers to the other, a drain pan associated with said outdoor heat exchanger for collecting frost removed from said outdoor heat exchanger, said refrigerant line including a drain pan heating portion between said flow control means and said indoor heat exchanger and in heat exchange relation with said defrost pan for warming said pan during flow of refrigerant through said refrigerant line from. said indoor heat exchanger to said outdoor heat exchanger.

4. A heat pump comprising a reversible cycle refrigerating system including a compressor, an indoor heat exchanger, flow control means, and an outdoor heat exchanger, refrigerant flow connections connecting said compressor, indoor heat exchanger, flow control means and said outdoor heat exchanger in series-flow relationship so that during operation of said heat pump on the heating cycle said compressor withdraws low pressure refrigerant from said outdoor heat exchanger and discharges high pressure refrigerant to said indoor heat exchanger, said outdoor heat exchanger operating as an evaporator during operation of said heat pump on the system containing high pressure refrigerant during opera tion of said heat pump on the heating cycle.

5. A heat pump comprising a reversible cycle refrigerating system including a compressor, an indoor heat exchanger, flow control means, and an outdoor heat exchanger, refrigerant fiow connections connecting said compressor, indoor heat exchanger, flow control means and said outdoor heat exchanger in series flow relationship so that during operation of said heat pump on the heating cycle said compressor Withdraws low pressure refrigerant from said outdoor heat exchanger and discharges high pressure refrigerant to said indoor heat exchanger, said outdoor heat exchanger operating as an evaporator during operation of said heat pump on the heating cycle and being subject to frosting during such operation, a drain pan for collecting frost and moisture removed from said outdoor heat exchanger, and means for raising the temperature of said pan above freezing temperatures during operation of said heat pump on the heating cycle, said means comprising a tubular portion of the refrigerating system which contains high pressure refrigerant during operation of said heat pump on the heating cycle.

References Cited in the file of this patent UNITED STATES PATENTS 2,472,792 Cohler June 14, 1949 2,654,227 Mufily Oct. 6, 1953 2,801,523 Hansen Aug. 6, 1957 2,801,528 Parcaro Aug. 6, 1957 

